APU

Question 1

What are the maximum altitudes for APU operation?

Answer 1

• Electric and bleed air 10,000’ (20,000’ CAs emergency authority
• Bleed air only 17,000’
• Electric only 41,000’

Question 2

What is the normal fuel supply for the APU?

Answer 2

• AC fuel pumps on Left side of manifold

* AC fuel pumps off Suction feed from No. 1 Main Tank

Question 3

If fuel is loaded in the center tank, which fuel pump should be operated to supply the APU?

Answer 3

L CTR — However, center tank fuel pump switches should be positioned ON only if center tank quantity exceeds 1000 lbs, and flight deck is attended.

Question 4

What is the electrical power source for the APU starter?

Answer 4

• AC power available AC Transfer Bus 1

* No AC power available Battery

Question 5

How long should the APU be operated before using it as a bleed source?

Answer 5

1 minute

Question 6

How long may the APU start cycle take?

Answer 6

2 minutes

Question 7

What is maximum altitude for APU start?

Answer 7

41,000’

Note: With Loss of Both Engine Driven Generators (QRH 6.4), APU start is not recommended above 25,000’

Question 8

To increase thrust above idle (i.e. after engine start), the APU Bleed Valve must be closed if __________.

Answer 8

• Engine 1 Bleed ON, or

* Engine 2 Bleed ON or external air connected and Isolation Valve OPEN

Question 9

To increase thrust above idle (i.e. after engine start), the APU Bleed Valve must be closed if __________.

Answer 9

• Engine 1 Bleed ON, or

* Engine 2 Bleed ON or external air connected and Isolation Valve OPEN

Question 10

APU load shedding during engine start:

Answer 10

Maintains bleed air, sheds elec load if required

Question 11

APU load shedding other than engine start:

Answer 11

Maintains elec load, reduces bleed air if required

Question 12

APU load shedding in flight (as only elec source):

Answer 12

All galleys and main buses may shed, then IFE buses shed if required to keep electrical load within limits

Question 13

APU load shedding in flight (as only elec source):

Answer 13

All galleys and main buses may shed, then IFE buses shed if required to keep electrical load within limits

Question 14

What conditions cause the APU to automatically shut down?

Answer 14

• LOW OIL PRESSURE (Light)
• FAULT (Light)
• OVERSPEED (Light)
• APU Fire (Switch)
• EGT exceedance (gauge)
• High oil temperature (no indication)
• Fuel Control Unit failure (no indication)

Question 15

When will LOW OIL PRESSURE, FAULT, or OVERSPEED Lights extinguish, if illuminated when APU Switch placed in OFF?

Answer 15

After 5 minutes

Question 16

If the FAULT Light extinguishes 5 minutes after APU Switch placed in OFF, may a restart be attempted?

Answer 16

Yes

Question 17

May the APU be started or operated with the MAINT Light illuminated?

Answer 17

Yes, but only if needed (make AML entry)